Chimney Swift Chaetura pelagica
As suggested by the common name, these birds are rapid fliers that commonly nest and roost in chimneys. Swifts are not members of the order Passeriformes; along with hummingbirds, they comprise the order Apodiformes, a term that refers to their very small feet. Swifts do not perch, but instead use the curved claws on their tiny toes to cling to vertical surfaces, with strong shafts protruding from their tail feathers serving as props. At one time, these birds were believed to be a type of swallow, but in the 1800s, swifts were placed in the genus Chaetura, a combination of two ancient Greek words meaning spine and tail. Pelagica is derived from another Greek word that probably referred to their wandering lifestyle rather than implying an association with oceans. Chimney swifts breed in southeast Canada on down through the eastern half of the United States. They typically arrive in Maine in May, departing in August/September for the wintering ground in the Amazon basin portions of South America.
Among the most aerial of birds, swifts spend much of their day on the wing hunting flying insects. They are likely to be seen near dusk as they approach the chimneys in which they will spend the night; from the ground, they are said to resemble flying cigars. Sometimes their high-pitched twittering is heard before they are noticed in the sky. Swifts even bathe and drink on the wing by flying low enough over the surface of a pond to dip their beaks in the water or slap the water with their bellies.
Chimney swifts probably once nested in caves or hollow trees, but they took advantage of the many chimneys built during the European settlement of North America. In more recent times, traditional unlined brick chimneys are increasingly rare. Declining population numbers have prompted some effort to construct artificial chimneys made of wood and/or cinder block, but these structures may not be widely used. Some swifts have been known to nest in old outbuildings such as barns, sheds, etc.There is only one nest per chimney. Unmated birds may occasionally share a chimney with a nesting pair, but more often, they roost communally in a chimney that does not host a nest. Chimney swifts are very social birds, with communal roosts increasingly large as pathways from northern areas converge during fall migration.
Chimney swift nests are made of small twigs that are glued to one another and to the inside chimney wall with a sticky salivary secretion. The twigs are woven together in a shape that resembles half of a small shallow bowl, usually 5-15 feet from the top of the chimney. Both parents build the nest, with egg-laying often beginning before the nest is finished. There are usually 4-5 eggs, which are incubated by both parents.
Both parents brood and feed their young, which hatch naked, blind, and helpless, requiring approximately one month to mature. Their eyes open relatively late in the developmental process, about 2 weeks after hatching. Because their feet develop more quickly, some young birds leave the nest and cling to the chimney wall before their eyes are open. If the clutch does not outgrow the nest sooner than that, visually-capable young would leave the nest at around 3 weeks. Begging calls of the young can be loud and raucous, sometimes startling home-owners who had not previously been aware of the swift family living in the chimney! Videos of nestling swifts near mealtime can be found in the Acute Care and Sunroom portions of our Facilities page.
Once out of the nest but before leaving the chimney, young birds exercise their wings by vigorously flapping while clinging to the wall; they are able to fly surprisingly well upon leaving the chimney at 28-30 days. Fledglings are also able to capture their own food in their first flight, and once having left the chimney, are no longer fed by their parents. Some family groups remain intact and roost together for a time in the nest chimney, but soon enough, families from nearby chimneys will converge on ever-larger staging chimneys as fall migration gets underway.
Nest failures may occur if prolonged periods of cold, rainy weather reduce insect availability. Additionally, nests may be dislodged from the chimney wall by heavy rains or may lose their attachment to walls that had been heavily coated with soot or creosote prior to nest construction. Birds that fall with the nest may be discovered cold, hungry, and possibly injured on the floor of a fireplace or behind the clean-out door at the bottom of the chimney. In some cases, older birds can be encouraged to climb up the chimney walls to rejoin their parents, but younger ones are truly orphaned, and should be taken by homeowners to a rehabilitator with the expertise required to rear them successfully.
Chimney Swift populations have declined in recent decades, likely due in part to waning numbers of insects. Although Chimney Swifts are not currently listed as threatened or endangered, here in Maine, they are classified as a Species of Special Concern, which means that they are vulnerable to becoming threatened or endangered.
If you are lucky enough to have swifts setting up housekeeping in your chimney, you can help them by having your chimney cleaned early in the spring, before nesting season. Click here for some excellent information from a conservation group in London, Ontario about being a Chimney Swift landlord.
More information about their natural history can be found at https://www.allaboutbirds.org/guide/Chimney_Swift